What is known as a vector dipole is known for example from the prior publication WO 00/39894. The construction thereof appears to be comparable to a dipole square. However, owing to the specific configuration of the dipole antenna in this prior publication and the particular way of feeding this dipole antenna, it operates in a similar manner to a crossed dipole which radiates in two polarization planes which are perpendicular to one another. In terms of its construction, it is rather square-shaped as a result of the outer contour configuration thereof in particular.
WO 2004/100315 A1 discloses a further configuration of the aforementioned vector dipole, in which the entire faces of each radiator half of one polarization can be closed to a large extent.
Dipole antennas of this type are conventionally fed in such a way that one dipole or radiator half is DC connected (i.e. galvanically) to an outer conductor, whereas the inner conductor of a coaxial connection cable is DC connected to the second dipole or radiator half (i.e. again galvanically connected). In each case, power is fed to the end regions of the dipole or radiator halves facing towards one another.
It is known from WO 2005/060049 A1 to feed the outer conductor by means of a capacitive outer conductor coupling. The support means or each associated half of the support means of the radiator arrangement can for this purpose be coupled to ground capacitively at the foot region or the base of the support means (in this case the outer connector of a coaxial feed line is generally preferably connected electrogalvanically to the reflector underneath the base of the support means).
A conventional, i.e. known from the prior art, feed means of a dipole of this type is shown in a sectional view in FIG. 1a, in particular for a radiator arrangement 1 which is specifically composed of a dipole 1′ and also comprises two radiator halves 1a or 1b, i.e. specifically two dipole halves 1′a and 1′b. The sectional view in FIG. 1a shows that this radiator arrangement 1 can be arranged on a reflector 105 for example in such a way that the radiator arrangement 1 is DC (i.e. galvanically) connected, via its base 7 at the bottom thereof, to an electrically conductive reflector 105 (which forms the ground or ground surface 5). A capacitive coupling can be produced if an insulating layer 21 is arranged between the base 7 and the reflector 105. If the electrically conductive base of the radiator device is galvanically isolated from the ground or reflector surface by an insulating layer, an electrogalvanic connection to the support means can, if desired, be produced by DC (i.e. galvanically) coupling the base 7 of the support means 9, which supports the dipole halves 1′a, 1′b, to ground.
Likewise, the half 9′, shown for example on the left in FIGS. 1a and 1b, of the support means 9 (which is formed as a hollow cylinder in the embodiment shown) could be extended through a hole in the reflector to the lower side or rear of the reflector or could at least terminate in the region of the recess or hole in the reflector in such a way that (when the support means is galvanically isolated from the reflector, for example by using an insulator provided between the reflector and the base of the support means of the radiator device) a first feed line (in particular in the form of an outer conductor of a coaxial cable) is in this case preferably electrogalvanically connected to one half 9′ of the support device 9 at the height of the conductor plane or the reflector in order to thereby feed the first dipole or radiator half 1a, 1′a as is known from WO 2005/060049 A1.
As can be seen from FIG. 1a and from the cross-section in FIG. 1b (FIG. 1b thus being a cross-section along the line II-II in FIG. 1 and again showing a dipole antenna known from the prior art), an axial hole 11′, which ultimately represents an outer conductor of a coaxial line, is provided in one of the rather tubular halves 9′ of the support means 9, an inner conductor 13 for feeding the radiator arrangement extending from the rear of the reflector in the direction of the second radiator half 1b in a feed plane 15 which is at a distance from the reflector plane or the base 7 of the radiator arrangement and is located closer to the radiator halves 1a and 1b and in which the inner conductor 13 can be DC connected, i.e. galvanically, to the second radiator half 1b at the feed point 17 for example. If an outer conductor were laid instead, i.e. a coaxial feed cable were used, the outer conductor of a coaxial cable of this type would be arranged for example in the hole 11′, the outer conductor then being able to be galvanically connected to the first radiator half 1a, for example at the approximate height of the feed plane 15. However, as mentioned, the half 9′ in question of the support means 9 may itself be used as an outer conductor line.
In a modified embodiment disclosed in WO 2005/060049, an axial hole 11″ is also provided in the second half 9″ of the support means 9 in such a way that a coaxial line arrangement is again formed, namely with an inner conductor 13 which extends from a matching network on the lower side of the reflector 105 via the first hole 11′ in the first half 9′ of the support means 9, thus forming a first inner conductor portion 13a, the inner conductor 13 then transitioning via an inner conductor or connection portion 13b, which extends at least approximately parallel to the reflector 105, into a third inner conductor portion 13c which passes from above into the second hole 11″ of the second half 9″ of the support means 9 and terminates freely approximately in the lower third of the support means 9 without contacting the electrically conductive support means 9. This is preferably achieved by using an insulator which is inserted in the holes 11′, 11″ is penetrated by the inner conductor 13 and is held thereby. In other words, the central inner conductor portion 13b is not galvanically connected to the associated dipole half 1b, 1′b at the feed point 17 but an inner conductor coupling is formed at this point instead.
A further device of the prior art is known from U.S. Pat. No. 4,668,956. This prior publication discloses a dipole antenna which in one embodiment comprises two dipole halves and in a further embodiment comprises two dipoles which are positioned so as to be offset relative to one another by 90°. Each dipole antenna comprises a tubular support means which is electrogalvanically connected to the reflector. Guided inside this support means, which serves as an outer conductor, is an inner conductor which projects from the rear of a hollow cylindrical support means and is fed at that point. At the height of the dipole halves, the inner conductor is guided approximately parallel to the reflector plane in the direction of the second half of the hollow cylindrical support means so as to then run back towards the reflector inside the second hollow cylindrical support means. The inner conductor terminates therein at a distance from the reflector plane and is electrogalvanically connected to the hollow cylindrical, electrically conductive support half via a short circuit element.
An electrogalvanically conductive lug, which projects parallel to the reflector plane and on which the dipole halves engage, is arranged on each of the two hollow cylindrical support means at the height of the end remote from the reflector.
The object of the present invention is to form, on the basis of the prior art mentioned at the outset, a dipole-shaped or dipole-like radiator arrangement which achieves even greater bandwidth.
The object is achieved according to the invention by the features specified in claim 1. Advantageous embodiments of the invention are specified in the sub-claims.
According to the invention, it is now provided that the inner conductor, which in the state of the art terminates freely inside the second half of the support means, is extended and DC connected (i.e. galvanically) to ground potential. In other words, one of the ends of the inner conductor is connected to the feed network (as in the prior art), whilst the other end of the inner conductor is now DC connected to ground.
This completely astonishing construction enables a marked improvement in the bandwidth of a radiator of this type to be achieved. In this case, the radiator is fed by a non-galvanic inner conductor feed means, it thus being possible to also use different materials (such as aluminium, a plastics material provided with a metal-coated surface, etc.) for the radiator, since no solder connections are required.
In contrast to the solution according to U.S. Pat. No. 4,668,956, the invention is based on a dipole-shaped or dipole-like radiator arrangement which radiates for example in one or two polarization planes, the radiator arrangement, comprising the dipole and/or radiator halves and the support means, including the base, as a whole being electrically conductive, but is nevertheless galvanically isolated via the reflector or ground plane, i.e. is preferably capacitively coupled to the ground or reflector surface. In addition, the end of the inner conductor, which is guided back towards the ground or reflector surface (i.e. the end opposite to that to which an appropriate signal is fed), is, according to the invention, not electrogalvanically connected to the support means, which is hollow cylindrical in form for example and encloses the inner conductor, but is connected to the ground and/or reflector surface.
In a particularly preferred embodiment, the base of the support means of the radiator arrangement is capacitively coupled to the reflector or to ground.
However, it is also possible to connect the base of the support means of the radiator galvanically to the reflector or ground.
Even if the base of the support means of the radiator arrangement is coupled capacitively to ground or to the ground surface, the length of the inner conductor and thus the height of the feed plane which is at a distance from the reflector or ground plane is generally selected in such a way that said feed plane is approximately at the height of the dipole or radiator halves. This feed plane is often positioned somewhat lower. The feed plane may for example preferably be located at any height between λ/10 below the radiator plane and λ/6 above the radiator plane, preferably however not more than λ/10 above the radiator plane. In this case, λ represents a wavelength of the frequency band to be transmitted, preferably approximately the average wavelength of the frequency band to be transmitted.
The height of the radiator may be in the conventional range of λ/4 over ground (i.e. the reflector or ground). This height should in any case preferably not fall below a value of λ/10. In principle, there is no upper limit so the radiator height may in principle be any desired multiple of λ (especially since a radiator has a radiation pattern even if there is no reflector). However, λ preferably only represents a wavelength from the frequency band to be transmitted, preferably at an average frequency of the frequency band to be transmitted.